1. Field of the Invention
The present invention relates to polysilanes, polysiloxanes, and silicone resist materials that contain these compounds, and more particularly to silicone resist materials that make it possible to form fine resist patterns that are used in the manufacture of integrated circuits for semiconductor elements.
2. Description of the Prior Art
In the manufacture of electronic parts for semiconductor elements, integrated circuits, and so on) fine processing techniques by means of photolithography has been used widely heretofore. The photolithographic techniques comprise a resist process and a etching process. In the resist process a desired resist pattern is formed by spreading an appropriate resist material over a single crystal silicon wafer or the like, and then irradiating it with ultraviolet rays or the like using a masking plate with desired pattern on the resist material, or irradiating it directly with electron beam using electron beam lithography system. In the etching process the film of SiO.sub.2, Al or the like which is the foundation film is processed by the use of the resist pattern thus obtained.
In the fine processing techniques, accuracy of the products is dominated substantially by the performances of the photoresist which is being used, for example, by its resolving power on the substrate, its accuracy of the photosensitivity, its adhesivity to the substrate, and others.
For this reason, various kinds of exposure technique, resist material, and so forth have been proposed in order to form resist patterns with excellent properties. In recent years, however, the processing techniques are being used in a multitude of modes so that resist materials that can be easily and quickly processed are being desired on the one hand.
On the other hand, photosensitive composites have been known as resist materials that are capable of forming high precision resist patterns. However, along with the diversification of functions and advancement of the electronic instruments, there has been an increased demand for a further miniaturization of patterns in order to realize an increase in the density and the degree of integration of the devices.
Now, in the existing monolayered resist method in which a single resist layer is formed over a wafer or the like, there exist various kinds of problems that become obstructions to the miniaturization of the resist patterns. Namely, the degree of reduction in the dimension of the integrated circuits in the longitudinal direction has not been as large as that in the lateral dimension, so that the ratio of the height to the width of the resist patterns has necessarily been large. Consequently, the control of the changes in the dimensions of a resist pattern on a wafer that has a complex step structure has become increasingly difficult with the progress in the miniaturization of the patterns.
Further, in various kinds of exposure systems, there are generated problems accompanying the reduction in the minimum dimensions. Thus, for instance, in the case of exposure with light, interference of the reflected light due to the level difference in the substrate is becoming to affect strongly the accuracy in the dimensions. Moreover, in the case of exposure with electron beams, it is becoming impossible to increase the ratio of the height to the width of the fine resist patterns, due to the proximity effect that is generated by the backscattering effect of electrons.
Now, it was discovered that these various kinds of problems can be resolved by adopting the multilayered resist system. The multi-layered resist system is described, for instance, in Solid State Technology, 74 (1981), but there are also published numerous studies on the system elsewhere.
In the multi-layered resist system, the most widely in general use currently is the resist system with three layer structure. This system consists of a bottom layer that serves to smooth out the steps in the substrate and to prevent the reflection from the substrate, an intermediate layer that functions as a mask in etching the bottom layer, and a top layer that serves as a photosensitive layer. Although the three-layered resist system possesses an advantage over the monolayered resist method in that it enables fine patterning, the system has a drawback in that the number of processes required up to the pattern formation has to be increased.